The present invention relates to a method and an apparatus for manufacturing a thick-walled bent pipe.
As for a metal elbow for piping, one with an elbow body 111 being attached to a piping block 113 or the like with a fastening nut 112 as shown in FIG. 8, is used conventionally. Both ends of the elbow body 111 are threaded, and one thread is screwed into the piping block 113 or the like and fastened with the nut 112, while a pipe not shown is attached to the other thread. The elbow body 111 can be freely oriented to the piping and fixed by being fastened with the nut 112. The elbow body 111 is provided with parallel plane portions 111s and 111s so that the elbow body 111 can be fixed with a spanner or the like when it is attached. Further, the elbow body 111 is bent at almost the right angle, which reduces the protruding amount from the piping block 113 or the like, thus requiring less piping space.
In a section of the elbow body 111, two fluid paths 111d and 111d cross each other at almost the right angle as shown in FIG. 9. Further, since the elbow needs to be threaded, a margin to cut needs to be secured, which makes a material for the elbow thick-walled. In addition, it is necessary to secure pressure resistance of an elbow in order to respond to high-pressurization of the fluid devices in recent years, and the wall thickness of the elbow body 111 after being worked becomes larger.
Accordingly, it is difficult to manufacture the elbow body 111 as shown in FIG. 9 by bending a thick-walled metal pipe at a small radius, since the pipe is crushed or the wall thickness of the pipe is reduced. Thus, a material of the elbow is made by cutting out a thick metal plate and forming it into a right-angle elbow, then the material is drilled from both end sides thereof to make the fluid passages 111d and 111d crossing each other at almost the right angle, and thereafter screw thread cutting is performed for both ends to thereby manufacture the elbow body 111.
However, in the above manufacturing method, the process of cutting the material includes two drilling operations and two screw thread cutting operations, which results in too many working steps, and thus the number of steps of preparing the material is large. Further, burrs caused by drilling occur at a crossing portion of the fluid passages 111d and 111d crossing each other at almost the right angle, which are made by drilling. Thus, an operation for removing the burrs that have occurred has to be performed, and the deburring operation is not easy and takes time, since burrs in the small holes have to be removed. Further, many cutting operations increase cutting amount of the material, thus reducing yields. Consequently, manufacturing cost is increased.
In order to eliminate the above disadvantages, a method for manufacturing a curved pipe material described in Japanese Patent Laid-open No. 59-163024 as shown in FIG. 10 to FIG. 12B is proposed. An apparatus thereof has a presser die A and press bearer dies B and C for supporting guide shafts b and c symmetrically positioned and respectively attached below the presser die A so as to be rotatable and horizontally slidable by inserting though and supporting them by horizontally long holes p and q provided in corresponding support frames P and Q. Bearing portions 2b and 3c for securely supporting both end portions of a straight pipe-shaped semiprocessed product N, which is formed by performing predetermined forging or grinding for a round metal bar, are respectively formed on the press bearing dies B and C. With the apparatus as described above, a thick-walled curved pipe can be manufactured by placing the straight pipe-shaped semiprocessed product N on the press bearing dies B and C, and lowering the press presser die A to thereby press and bend the straight pipe-shaped semiprocessed product N.
However, the method of manufacturing the curved pipe material described in Japanese Patent Laid-open No. 59-163024 has the following disadvantages.
The straight pipe-shaped semiprocessed product N is provided with a pipe hole 1 and bulging parts for connection at both ends as shown in FIG. 12A. A pipe part 4 is provided with uneven wall thickness on an upper side and an lower side with wall thickness being made smaller on the upper side and larger on the lower side as shown in FIG. 12B. Accordingly, forging or grinding, and boring are performed to form the round bar-shaped material into the straight pipe-shaped semiprocessed product N as described above, thus requiring plenty of time to perform the working.
Further, when the straight pipe-shaped semiprocessed product N is pressed and bent, the press bearing dies B and C are moved transversely within the ranges of the horizontally long holes p and q to widen a space between them following the deformation of the straight pipe-shaped semiprocessed product N, while rotating as shown in FIG. 11. The moving amount is determined by an outer shape dimension and wall thickness dimension of the straight pipe-shaped semiprocessed product N, and the aforesaid moving amount varies according to the variations in the outer shape dimension and the wall thickness dimension of the straight pipe-shaped semiprocessed product N. Accordingly, the dimension of the straight pipe-shaped semiprocessed product N in a longitudinal direction thereof, that is, a dimension in the left and right direction in FIG. 11 varies within the range of the horizontally long holes p and q in which the dies B and C move transversely to widen the space between them. Specifically, the longitudinal dimension of the straight pipe-shaped semiprocessed product N changes and varies. If the dimension of the straight pipe-shaped semiprocessed product N varies, positioning becomes difficult when machining is performed in the next process, which is not preferable.
The present invention is made in view of the above disadvantages, and its object is to provide a method and an apparatus for manufacturing a thick-walled bent pipe capable of manufacturing an elbow material for piping with higher size accuracy with use of a thick-walled pipe material.
In order to attain the above object, a method for manufacturing a thick-walled bent pipe according to the present invention has a configuration including the steps of:
placing a thick-walled metal pipe material of a predetermined length on a lower die including a pair of bottom dies having sliding surfaces each in a circular arc form and placed on slide surfaces of a lower guide;
pressing a middle portion in a longitudinal direction of the thick-walled metal pipe material by means of an upper die including an upper guide having a guide surface in a circular arc form for guiding the lower die, and a presser die;
rotating the bottom dies respectively while they are facing to each other, by lower end portions of the bottom dies respectively abutting to and sliding along the slide surfaces at the same time when the sliding surfaces abut to and slide along the guide surface in the circular arc form to thereby bend the thick-walled metal pipe material.
According to the above configuration (a first configuration of the method), a pair of bottom dies of the lower die rotate along the guide surface in the circular arc form of the upper die having a center of rotation while they are facing to each other. Thereby, changes in the distances between both the end surfaces of the thick-walled pipe material and the center of rotation at the start of bending and at the completion of bending are reduced, thus making it possible to form a thick-walled elbow material with less variations in size.
As a result, an elbow material can be provided by cutting the thick-walled pipe, thus making it unnecessary to prepare a forged material. Further, since a thick-walled pipe can be used, drilling for making small holes to form fluid passages is unnecessary, and deburring at the crossing portion of the drilled holes, which is conventionally performed, is made unnecessary. Further, since the thick-walled pipe has a round outer shape, the margin to cut for screw thread cutting is reduced. Accordingly, a special drill is not needed, and the time required for working, and tool cost can be substantially reduced, and the yield of the material can be improved.
Further, the hole in the thick-walled elbow material thus formed is not a crossing drilled hole as in the conventional art, but is a smoothly curved hole, thus making it possible to reduce pressure loss of a fluid passing through the elbow. Further, the bending angle can be set at will by adjusting the descending stroke of the upper die, thus making it easy to manufacture many kinds of thick-walled elbow materials with different bending angles.
Further, the method for manufacturing the thick-walled bent pipe may have a configuration in which
both end surfaces of the thick-walled metal pipe material are restrained by a stopper provided in the bottom dies.
According to the above configuration (a second configuration of the method), bending work is performed with the thick-walled pipe material being restrained so that it has a size set by the upper die, the lower die and the stopper, thus making it possible to form the thick-walled elbow material of accurate size.
Further, the method for manufacturing the thick-walled bent pipe may have a configuration in which,
the stopper includes a first stopper and a second stopper which are allowed to slide in the bottom dies in the longitudinal direction of the thick-walled metal pipe material, the first stopper and the second stopper are guided to be closer to the guide surface in the circular arc form as the first stopper and the second stopper are at an upper portion of the upper guide by stopper guide surfaces provided on the upper guide, and the first stopper and the second stopper push both the end surfaces of the thick-walled pipe material toward a center portion in the longitudinal direction when the bottom dies rotate.
According to the above configuration (a third configuration of the method), the first stopper and the second stopper are respectively slidable in the longitudinal direction. Further, one end surfaces of the first stopper and the second stopper abut to and slide along the stopper guide surfaces so that they are closer to the guide surface in the circular arc form of the upper guide as they are at the upper portion of the upper guide. Thus, the other side surfaces of the first stopper and the second stopper can push against both the end surfaces of the pipe material during bending while they are serving as the stoppers for both the end surfaces of the pipe material.
As a result, the pipe material is accurately formed into the thick-walled elbow material of a size set by the one end surface of the first stopper and the one end surface of the second stopper respectively abutting along the stopper guide surfaces. Further, by replacing the fist stopper and the second stopper with those of different lengths, various kinds of thick-walled elbow materials of different sizes can be manufactured with one kind of dies.
An apparatus for manufacturing a thick-walled bent pipe according to the present invention has a configuration including:
a lower die including a pair of bottom dies having sliding surfaces each in a circular arc form;
an upper die including an upper guide having a guide surface in a circular arc form for guiding the lower die, and a presser die; and
a lower guide having slide surfaces for placing the bottom dies thereon, and a configuration in which
the bottom dies are allowed to rotate respectively while they are facing to each other, by lower end portions of the bottom dies respectively abutting to and sliding along the slide surfaces at the same time when the sliding surfaces respectively abut to and slide along the guide surface in the circular arc form in connection with descent of the upper die.
According to the above configuration, the same operational effects as in the first configuration of the above method can be obtained.
Further, the apparatus for manufacturing the thick-walled bent pipe may have a configuration in which,
the bottom dies are provided with a stopper abutting to both end surfaces in a longitudinal direction of a material to be worked. According to the above configuration, the same operational effects as in the second configuration of the above method can be obtained.
Further the apparatus for manufacturing the thick-walled bent pipe may have a configuration in which,
the stopper includes a first stopper and a second stopper which are allowed to slide in the bottom dies in the longitudinal direction of the material to be worked;
the upper guide is provided with stopper guide surfaces; and
the stopper guide surfaces respectively guide the first stopper and the second stopper so that the first stopper and the second stopper are closer to the guide surface in the circular arc form as the first stopper and the second stopper are at an upper portion of the upper guide.
According to the above configuration, the same operational effects as in the third configuration of the above method can be obtained.